• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.292-296
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• 2000

본 논문에서는 임펄스 잡음과 다중경로 레일리 페이딩이 함께 존재하는 최악의 채널 환경에서 비동기 DS/CDMA BPSK 시스템의 오율식을 유도하고 수치계산 하여 BER 성능을 분석하였다. 그 결과, 비교적 낮은 신호 대 잡음 전력비 영역에서 시스템의 BER 성능은 임펄스 잡음의 영향으로 크게 열화되지만 페이딩의 영향은 거의 없다. 그러나, 임펄스 잡음의 영향이 작아지는 높은 신호 대 잡음 전력비에서는 페이딩에 의해서 BER 성능이 결정된다. 다중사용자의 간섭도 낮은 신호 대 잡음 전력비 영역에서는 BER 성능에 거의 영향을 미치지 못하지만 높은 신호 대 잡음 전력비 영역에서는 BER 성능을 좌우한다 그러나, 실제 이동통신 시스템에서는 비교적 낮은 신호 전력을 사용하므로, 임펄스 환경에서 페이딩을 경감하기 위한 방법이나, 다중사용자 간섭을 줄이기 위한 기법을 적용하더라도 성능 개선이 거의 되지 않는다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.727-731
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• 2001

된 논문에서는 임펄스 잡음과 다중접속간섭(MUI) 및 나카가미 페이딩 환경으로 모델링되는 FH/CDMA 시스템을 제안하고 이의 성능을 분석하였다. 결과에 의하면 FH-CDMA 시스템은 잡음이나 페이딩의 영향보다는 여러명의 사용자가 같은 시간에 같은 주파수를 사용함으로 인한 충돌과 임펄스 잡음에 의해 더 큰 영향을 받는다. 성능 개선기법으로 다이버시티 기법과 에러정정 부호화 기법을 사용함으로써 페이딩과 다중접속 간섭에 대하여 어느 정도의 개선효과를 보이지만 임펄스 잡음의 영향으로 무선 데이터 통신을 만족하는 시스템 성능을 가질수 없었다. 따라서 한번의 재전송만을 고려한 Truncated Type-II Hybrid ARQ기법을 동시에 채용함으로써 다중접속 간섭과 임펄스 잡음에 의한 전송에러를 감소시키고 고신뢰도의 무선 데이터 통신을 만족하는 시스템 성능을 보임을 알 수 있었다.

• Journal of the Institute of Convergence Signal Processing
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• v.2 no.4
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• pp.65-70
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• 2001

In this paper a new scheme combining the turbo coder with parallel interference canceller, which effectively mitigates the effects of multiple access interferences and Ralyeigh fades in the DS-CDAM mobile communication systems is proposed Using the Monte-Carlo simulation, the performance of this scheme in terms of the number of users and signal to noise ration under AWGN and Ralyeigh fading environment is analyzed. The results of simulations show that the proposed scheme outperforms conventional CDMA receiver systems over Rayleigh fading as well as AWGN.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.11
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• pp.1254-1261
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• 2007

Mc-OFDM(Multi code-Orthogonal Frequency Division Multiplexing) modulation has been developed for high-speed data transmission over wireless channels. However, this system suffers critical problem from relatively high PAPR(Peak to Average Power Ratio). To reduce PAPR, we suggest a new technique, called Mapping using (N+1)PSK and demonstrate the performance of mapped Mc-OFDM system. On the other side, in OFDM system, each sub-carrier experiences different fading, thus some sub-carriers may be completely lost because of deep fade. To solve a above mention problem, we propose cooperative communications that improve the reliability of sub-carriers through spatial diversity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1050-1055
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• 2001

In this paper we analyze the performance of 2-D PSAM for wireless OFDM systems. We apply the analysis of single-carrier PSAM to the 2-D time-frequency lattice of OFDM. To estimate channel fading, we use interpolation filter which minimizes the average power of error as compensation method and analyze the affects on the system performance of the pilot symbol pattern on the 2-D time-frequency lattice. Finally according to the CP and the Doppler frequency, we analyze the performance of 2-D PSA-16QAM for OFDM systems over frequency selective Rayleigh fading channel model.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.5
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• pp.974-979
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• 2009

The BER performance of a MIMO detection scheme on frequency selective Rayleigh fading channels is analytically discussed. The presented MIMO detection scheme consists of temporal and spatial combiners followed by a ZF detector. It is shown that for a MIMO system with $N_T$ transmit antennas, $N_R$ receive antennas, and L resolvable multipath components, it achieves the diversity order of $LN_R-N_T+1$. In frequency selective Rayleigh fading channels, an analytical error rate expression of the systems is also provided and the analytical error performance is compared with the simulated results.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.8
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• pp.301-306
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• 2003

This paper proposes a novel detection scheme using a radial basis function (RBF) network in a multi-input multi-output (MIMO) environment. In order to evaluate the performance of the proposed MIMO-RBF receiver, simulations are performed over the rich-scattering fading channel. Simulation results confirm that the proposed scheme shows the similar bit-error rate (BER) performance of a maximum likelihood detection (MLD) and outperforms Vertical-Bell Laboratories Layered Space-Time using minimum-mean-square-error nulling (VBLAST-MMSE) as well as VBLAST using zero-forcing nulling (VBLAST-ZF). Moreover, we investigate the effect on the performance of the number of RBF center with two modulation formats (BPSK and QPSK) and different number of transmit and receive antennas. The performance of the proposed detector is verified with respect to an initialization-rate of RBF centers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.7
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• pp.1667-1676
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• 1998

It is known that adaptive minimum mean square error (MMSE) receivers exhibit better performance than coventional single-user code division multiple access (CDMA) receivers in fixed (or static) channels and have the simple structure compared to other multi-user CDMA receivers. In practice, the radio channels are fading channels where the amplitude and phase of the received signal are time-varying and the sufficient signal-to-noise ratio is not always guaranteed. Thus, the performance of adaptive MMSE receivers is severely degraded in fading environments. We propose a new structure and adaptation algorithm for an adaptive MMSE receivers. Based on computer simulation results, it is observed that the proposed receiver demonstrates substantial performance improvement over currently available adaptive MMSE receivers in fading environments.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.64-68
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• 2010

In this paper, we studied the novel synchronization algorithm for cooperative communication system over fading. We research mainly on the decode-and-forward scheme. Also, we inserted spreading sequence in origin data frame to control efficiently data synchronization. In mobile station, inserted spreading sequence in data frame passed through the corelation process. We had decide the delay value of received data through result of correlation process. In simulation, We applied that channel gain of three node had different value in various fading environment. Finally we will be possible to control the received data synchronization using result of corelation value in each node between relay to mobile station and base station to mobile station. The results of this paper can be applicable to the cooperative systems.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.336-340
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• 2001

In this paper we analyze the performance of 2-D PSAM for wireless OFDM systems. We apply the analysis of single-carrier PSAM to the 2-D time-frequency lattice of OFDM. To estimate channel fading, we use interpolation filter which minimizes the average power of error as compensation method and analyze the affects on the system performance of the pilot symbol pattern on the 2-D tine-frequency lattice. Finally according to the CP and the Doppler frequency, we analyze the performance of 2-D PSA-16QAM for OFDM systems over frequency selective Rayleigh fading channel model.